Definition of Done
In an agile development model, you and your team releases each takt software that your (interal and external) stakeholders can consume immediately. You and your team specify, design, develop and test these potentially shippable products during the sprint. Thus, one of the most important aspects for your agile development project is the question, when you should consider a development task as done.
Formalized Done Criteria that match with the characteristics of your development product help you with this release decision.